I suspect that you have some pointers to drive M on your C or your D.
Let's see if you can perform a System Image backup from just C to M
Now this is a system image backup and NOT a backup of data folders, although the system image backup will include folders.
The Win 7 terminology is very confusing.
For a backup which will enable you to restore your computer to a prior state, then the system image backup does everything for you. The "data" backup allows you to perform incremental updates of, for example, your documents library and produces zip files
To perform a system image backup, plain and pure, then when you start up Win 7 Backup and Restore, choose from the LEFT-HAND PANE,
choose Create a system image
Let me know how this goes.